Elastic wave element and ladder filter using same

ABSTRACT

Methods and apparatus for reducing electric loss in an elastic wave element. In one example, the elastic wave element includes a piezoelectric body having a upper surface, an interdigital transducer (IDT) electrode disposed on the piezoelectric body, a connection wiring disposed on the piezoelectric body and electrically connected to the IDT electrode, the connection wiring having a lower connection wiring and an upper connection wiring provided above the lower connection wiring, and a reinforcement electrode provided above the connection wiring, the reinforcement electrode being in contact with and electrically connected to the lower connection wiring.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit under 35 U.S.C. §119 and PCTArticle 8 of co-pending Japanese Patent Application No. 2014-028059filed on Feb. 18, 2014 and titled “ELASTIC WAVE ELEMENTS AND LADDERFILTERS USING SAME,” which is hereby incorporated herein by reference inits entirety for all purposes. This application also claims the benefitunder 35 U.S.C. §120 of co-pending International Application No.PCT/JP2015/000718 filed on Feb. 17, 2015 and titled “ELASTIC WAVEELEMENTS AND LADDER FILTERS USING SAME,” which is hereby incorporatedherein by reference in its entirety for all purposes.

BACKGROUND

FIGS. 1 and 2 illustrate an example of a conventional elastic waveelement 6000, which may be used in an electronic device such as awireless communication apparatus. FIG. 1 shows a plan view of theconventional elastic wave element 6000, and FIG. 2 shows a correspondingcross-sectional view taken along line B-BB of FIG. 1. As shown in FIGS.1 and 2, the conventional elastic wave element 6000 includes a firstinterdigital transducer (IDT) electrode 1000 and a second IDT electrode2000 both provided on the upper surface of a piezoelectric body 5000.The conventional elastic wave element 6000 further includes a connectionwiring 3000 connecting the first IDT electrode 1000 to the second IDTelectrode 2000, and a reinforcement electrode 4000 provided on theconnection wiring 3000. The reinforcement electrode 4000 is provided forreducing the electric resistance of the connection wiring 3000connecting the first IDT electrode 1000 to the second IDT electrode2000. In addition, the connection wiring 3000 includes a lowerconnection wiring 3002 and an upper connection wiring 3001. The upperconnection wiring 3001 is provided on the upper surface of the lowerconnection wiring 3002.

Japanese Patent Application Publication No. 2011-71912 describes anexample of such a conventional elastic wave element.

SUMMARY OF INVENTION

Aspects and embodiments are directed to an elastic wave element and aladder filter using the same.

In conventional elastic wave elements, such as that discussed above withreference to FIGS. 1 and 2, merely providing the reinforcement electrodeon the upper surface of the connection wiring is insufficient toadequately reduce the electric loss. Accordingly, embodiments of anelastic wave element according to the present invention may beconfigured to greatly reduce the electric loss in the connection wiringelectrically connected between the IDT electrodes, as discussed in moredetail below.

According to one embodiment, an elastic wave element comprises apiezoelectric body having an upper surface, an interdigital transducer(IDT) electrode provided above the piezoelectric body, a connectionwiring connected to the IDT electrode provided above the piezoelectricbody, the connection wiring having a lower connection wiring and anupper connection wiring provided above the lower connection wiring, anda reinforcement electrode provided above the connection wiring, thereinforcement electrode being in contact with and electrically connectedto the lower connection wiring.

In one example of the elastic wave element, the connection wiringincludes a hole electrode extending in a direction perpendicular to theupper surface of the piezoelectric body, the reinforcement electrodebeing electrically connected to the lower connection wiring via the holeelectrode. In one example, the hole electrode extends through the upperconnection wiring and the lower connection wiring, a first diameter ofthe hole electrode in the upper connection wiring being larger than asecond diameter of the hole electrode in the lower connection wiring.

The material of the lower connection wiring may be different from thematerial of the upper connection wiring. In particular, an oxygenaffinity of the material of the lower connection wiring may be less thanan oxygen affinity of the material of the upper connection wiring.

The reinforcement electrode may be in contact with and electricallyconnected to an upper surface of the lower connection wiring. In oneexample, the upper connection wiring is divided by the reinforcementelectrode in a cross section taken in a direction perpendicular to theupper surface of the piezoelectric body to provide first and secondupper connection wirings, the first and second upper connection wiringsbeing electrically connected to each other via the reinforcementelectrode. The elastic wave element may further comprise a thirdconnection electrode disposed on the piezoelectric body between thefirst and second upper connection wirings, the third connection wiringbeing covered with an insulation layer, and the reinforcement electrodeextending over the insulation layer. In another example, the lowerconnection wiring is divided by the reinforcement electrode in a crosssection taken in the direction perpendicular to the upper surface of thepiezoelectric body to provide first and second lower connection wirings,the first and second lower connection wirings being electricallyconnected to each other via the reinforcement electrode. The elasticwave element may further comprise a third connection wiring disposed onthe piezoelectric body between the first and second lower connectionwirings, the third connection wiring being covered with an insulationlayer, and the reinforcement electrode extending over the insulationlayer.

In one example, the IDT electrode includes a lower IDT electrode and anupper IDT electrode provided above the lower IDT electrode, a materialof the lower IDT electrode being identical to a material of the lowerconnection wiring, and a material of the upper IDT electrode beingidentical to a material of the upper connection wiring.

According to another embodiment, an elastic wave element comprises apiezoelectric body having an upper surface, a first interdigitaltransducer (IDT) electrode disposed on the piezoelectric body, a secondIDT electrode disposed on the piezoelectric body, a connection wiringdisposed on the upper surface of the piezoelectric body and electricallyconnected to the first IDT electrode and the second IDT electrode, theconnection wiring including a lower connection wiring and a upperconnection wiring disposed above the lower connection wiring, and areinforcement electrode disposed above the connection wiring, thereinforcement electrode being in contact with and electrically connectedto the lower connection wiring.

In one example, the lower connection wiring is formed of a firstmaterial and the upper connection wiring is formed of a second material,an oxygen affinity of the first material being less than an oxygenaffinity of the second material.

In another example, the reinforcement electrode is further in contactwith and electrically connected to the upper connection wiring. Theconnection wiring may further include a hole electrode extending throughthe upper connection wiring and the lower connection wiring in adirection perpendicular to the upper surface of the piezoelectric body.In one example, the hole electrode has a first diameter in the upperconnection wiring and a second diameter in the lower connection wiring,the first diameter being larger than the second diameter. Thereinforcement electrode is electrically connected to the lowerconnection wiring via the hole electrode.

In another example, the connection wiring, including both the upper andlower connection wirings, is divided by the reinforcement electrode in across section taken in a direction perpendicular to the upper surface ofthe piezoelectric body to provide first and second connection wirings,the first and second connection wirings being electrically connected toeach other via the reinforcement electrode. The elastic wave element mayfurther comprise a third connection wiring disposed on the piezoelectricbody between the first and second connection wirings, the thirdconnection wiring being covered with an insulation layer, and thereinforcement electrode extending over the insulation layer.

Another embodiment is directed to a ladder filter including the elasticwave element of any of the examples discussed above.

According to another embodiment, an elastic wave element comprises apiezoelectric body having an upper surface, a first interdigitaltransducer (IDT) electrode disposed on the piezoelectric body, a secondIDT electrode disposed on the piezoelectric body, a connection wiringdisposed on the upper surface of the piezoelectric body and electricallyconnected to the first IDT electrode and the second IDT electrode, andmeans for reducing electric loss in the connection wiring.

Still other aspects, embodiments, and advantages of these exemplaryaspects and embodiments are discussed in detail below. Embodimentsdisclosed herein may be combined with other embodiments in any mannerconsistent with at least one of the principles disclosed herein, andreferences to “an embodiment,” “some embodiments,” “an alternateembodiment,” “various embodiments,” “one embodiment” or the like are notnecessarily mutually exclusive and are intended to indicate that aparticular feature, structure, or characteristic described may beincluded in at least one embodiment. The appearances of such termsherein are not necessarily all referring to the same embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects of at least one embodiment are discussed below withreference to the accompanying figures, which are not intended to bedrawn to scale. The figures are included to provide illustration and afurther understanding of the various aspects and embodiments, and areincorporated in and constitute a part of this specification, but are notintended as a definition of the limits of the invention. In the figures,each identical or nearly identical component that is illustrated invarious figures is represented by a like numeral. For purposes ofclarity, not every component may be labeled in every figure. In thefigures:

FIG. 1 is a plan view schematically showing an example of a conventionalelastic wave element;

FIG. 2 is a cross-sectional view of the conventional elastic waveelement of FIG. 1 taken along line B-BB in FIG. 1;

FIG. 3 is a plan view schematically showing one example of an elasticwave element according to aspects of the present invention;

FIGS. 4A-D are cross-sectional views of examples of the elastic waveelement of FIG. 3 taken along line A-AA in FIG. 3;

FIG. 5A is a cross-sectional view of one example of a conventionalelastic wave element showing measurement conditions of a contactresistance value of the connection wiring;

FIG. 5B is a corresponding plan view of the example conventional elasticwave element of FIG. 5A;

FIG. 6A is a cross-sectional view of one example of an elastic waveelement showing measurement conditions of a contact resistance value ofthe connection wiring according to aspects of the present invention;

FIG. 6B is a corresponding plan view of the example elastic wave elementof FIG. 6A;

FIG. 7A is a cross-sectional view of another example of an elastic waveelement showing measurement conditions of a contact resistance value ofthe connection wiring according to aspects of the present invention;

FIG. 7B is a corresponding plan view of the example elastic wave elementof FIG. 7A;

FIG. 8 is a characteristic diagram showing measurement results of thecontact resistance value of the connection wiring corresponding to theexamples of FIGS. 5A-7B;

FIG. 9A is a cross-sectional view of an example of a conventionalelastic wave element showing measurement conditions of a resistancevalue per unit length of the connection wiring;

FIG. 9B is a corresponding plan view of the example conventional elasticwave element of FIG. 9A;

FIG. 10A is a cross-sectional view of one example of an elastic waveelement showing measurement conditions of a resistance value per unitlength of the connection wiring, according to aspects of the presentinvention;

FIG. 10B is a corresponding plan view of the example elastic waveelement of FIG. 10A;

FIG. 11A is a cross-sectional view of another example of an elastic waveelement showing measurement conditions of a resistance value per unitlength of the connection wiring, according to aspects of the presentinvention;

FIG. 11B is a corresponding plan view of the example elastic waveelement of FIG. 11A;

FIG. 12 is a characteristic diagram showing measurement results of theresistance value of the connection wiring corresponding to the examplesof FIGS. 9A-11B;

FIG. 13 is a circuit diagram of one example of a ladder filter accordingto aspects of the present invention; and

FIG. 14 is a characteristic diagram showing pass characteristics of theladder filter according to aspects of the present invention.

DETAILED DESCRIPTION

Certain aspects and embodiments are described below with reference tothe drawings and an exemplary elastic wave element 60.

FIG. 3 is a plan view schematically illustrating an embodiment of theelastic wave element 60. FIGS. 4A-D are cross-sectional views of variousexamples of the elastic wave element 60 taken along line A-AA in FIG. 3.

According to one embodiment, the elastic wave element 60 includes apiezoelectric body 50 made of a single crystal piezoelectric material. Afirst IDT electrode 10 and a second IDT electrode 20 are provided on theupper surface of the piezoelectric body 50. The elastic wave element 60further includes two reflectors 13 disposed adjacent the IDT electrodes10, 20 in the propagation direction of an elastic wave generated by thefirst IDT electrode 10 and the second IDT electrode 20. The elastic waveelement 60 further includes a connection wiring 30 electricallyconnecting the first IDT electrode 10 and the second IDT electrode 20,and a reinforcement electrode 40 provided on the upper surface of theconnection wiring 30 for reducing the electric loss of the connectionwiring 30. The first IDT electrode 10 has comb-shaped electrodes eachincluding a line-shaped first bus bar 12 and a plurality of firstelectrode fingers 11 perpendicularly extending with respect to the linedirection of the line-shaped first bus bar 12. The first IDT electrode10 is made of the opposing comb-shaped electrodes. Similar to the firstIDT electrode 10, the second IDT electrode 20 includes comb-shapedelectrodes each having a second bus bar 22 and a plurality of secondelectrode fingers 21. The first IDT electrode 10, the second IDTelectrode 20, the reflectors 13, the connection wiring 30, and thereinforcement electrode 40 may be formed by patterning a metallic thinfilm. Although not shown in the drawings, those skilled in the art willappreciate, given the benefit of this disclosure, that the elastic waveelement 60 according to certain embodiments may be improved in itstemperature characteristic by providing a dielectric layer that coversthe upper surfaces of the piezoelectric body 50, the first IDT electrode10, the second IDT electrode 20, the reflectors 13, the connectionwiring 30, and the reinforcement electrode 40.

In one embodiment, the connection wiring 30 includes an upper connectionwiring 31 and a lower connection wiring 32. The lower connection wiring32 and the reinforcement electrode 40 are in contact with andelectrically connected to each other so that the electric loss can begreatly reduced in the connection wiring 30. The electric loss may occurwhen an oxide film formed on the surface of the upper connection wiring31 and the lower connection wiring 32 during the thin film processingblocks the electrical connection between the connection wiring 30 andthe reinforcement electrode 40. In other words, the electricalresistance reduction effect of the connection wiring 30, which iseffected by providing the reinforcement electrode 40 as described above,may be lost or degraded by the presence of the oxide film. In view ofthe reasons as described above, certain aspects and embodiments addressthe oxide film formed on the surface of the connection wiring 30 andreduce the electric loss in the connection wiring 30 by reducing thecontact resistance between the connection wiring 30 and thereinforcement electrode 40.

According to one embodiment, the material forming the upper connectionwiring 31 and the lower connection wiring 32 may preferably be amaterial that is not likely to form an oxide film on the surface.Generally, the susceptibility to oxidation is represented by an oxygenaffinity. In addition, because the main cause of the electric lossreduction effect in the connection wiring 30 in one embodiment is theconfiguration in which the lower connection wiring 32 and thereinforcement electrode 40 are in contact with and electricallyconnected to each other, it may be preferable to allow the oxygenaffinity of the material forming the lower connection wiring 32 to beless than the oxygen affinity of the material forming the upperconnection wiring 31. The oxygen affinity of the material generallycorrelates with a standard free-energy, and the less the standardfree-energy (ΔG/kJmol⁻¹), the less the oxygen affinity. Representativematerials are exemplified by: Pt<Ru<Cu<Mo≈W<<Ti<Al<Mg listed inascending order of the standard free-energy.

It is to be appreciated that although a two-layer structure of upperconnection wiring 31 and the lower connection wiring 32 is described inat least one embodiment, the structure is not limited to two layers andmay be configured as three or more layers.

The configuration of the connection wiring 30 and the reinforcementelectrode 40 according to certain embodiments is described in detailbelow with reference to FIGS. 4A-D.

As shown in FIGS. 4A-D, according to certain embodiments, at least thelower connection wiring 32 and the reinforcement electrode 40 are incontact with and electrically connected to each other in the connectionwiring 30. The lower connection wiring 32, the upper connection wiring31, and the reinforcement electrode 40 are sequentially provided on theupper surface of the piezoelectric body 50. In addition, the connectionwiring 30 can be integrally and simultaneously formed with the first IDTelectrode 10 and the second IDT electrode 20 using thin film processing.Furthermore, it may be preferable to use the same configuration (e.g., avertically two-layer structure) and the same material for simplifyingthe manufacturing process.

Referring to FIG. 4A, in one embodiment, it is characteristic that theupper connection wiring 31 is divided by the reinforcement electrode 40,and the upper surface of the lower connection wiring 32 and thereinforcement electrode 40 are in contact with and electricallyconnected to each other. In addition, the upper surface and the sidesurfaces of the upper connection wiring 31 are in contact with andelectrically connected to the reinforcement electrode 40.

Referring to FIG. 4B, in another embodiment, in addition to thecharacteristics of the example shown in FIG. 4A, the lower connectionwiring 32 is also divided by the reinforcement electrode 40, and thepiezoelectric body 50 also has a surface in contact with thereinforcement electrode 40. The reinforcement electrode 40 may becharacterized by the configuration of being in contact with andelectrically connected to the side surfaces of the lower connectionwiring 32.

Referring to FIG. 4C, according to another embodiment, a hole electrode70 is provided extending in the direction perpendicular to the uppersurface of the piezoelectric body 50 through the upper connection wiring31 and the lower connection wiring 32, such that the lower connectionwiring 32 and the reinforcement electrode 40 are in contact with andelectrically connected to each other. In addition, with respect to thecross section of the hole electrode 70 taken along the directionparallel to the upper surface of the piezoelectric body 50, it may bepreferable to allow the cross-sectional area of the hole electrode 70provided in the lower connection wiring 32 to be less than thecross-sectional area of the hole electrode 70 provided in the upperconnection wiring 31, such that not only the side surfaces of the lowerconnection wiring 32 but also the upper surface thereof can be incontact with and electrically connected to the reinforcement electrode40. As a result, the contact area is greater to further reduce thecontact resistance.

It is to be appreciated that the shape of the hole electrode 70 is notlimited to the example shown in FIG. 4C, and may have anycross-sectional shape, including, for example, circular, rectangular,and the like. In addition, the cross section may be differentlyconfigured in the depth direction of the hole electrode 70. It is alsoto be appreciated that, although not shown in the drawings, the holeelectrode 70 may be provided only in the upper connection wiring 31 forthe upper surface of the lower connection wiring 32 to be in contactwith and electrically connected to the hole electrode 70.

Referring to FIG. 4D, there is illustrated another configuration of theconnection wiring according to certain examples. In this configuration,when one connection wiring 30 divided by the reinforcement electrode 40is designated as a first connection wiring 100 and the other connectionwiring 30 is designated as a second connection wiring 110, a thirdconnection wiring 120 is provided on the upper surface of thepiezoelectric body 50 between the first connection wiring 100 and thesecond connection wiring 110. The third connection wiring 120 is coveredwith an insulation layer 80. As a characteristic configuration, thereinforcement electrode 40 may cross with an overpass of the thirdconnection wiring 120 via the insulation layer 80, and the firstconnection wiring 100 and the second connection wiring 110 are incontact with and electrically connected to each other. The thirdconnection wiring 120 may be an electrode that has a potential differentfrom that of the first connection wiring 100 or the second connectionwiring 110. In one example, the third connection wiring 120 may beintegrally and simultaneously formed with the first connection wiring100 and the second connection wiring 110. It may be preferable to adoptthe same configuration (e.g., a vertically two-layer structure) and thesame material for simplifying the manufacturing process.

The contact resistance between the connection wiring 30 and thereinforcement electrode 40 will be described below, comparingembodiments of elastic wave element 60 with a conventional elastic waveelement, and with reference to FIGS. 5A-7B, which illustrate examples ofmeasuring the contact resistances in the connection wiring 30 and thereinforcement electrode 40.

FIG. 5A is a cross-sectional view and FIG. 5B is a plan viewcorresponding to the configuration of the conventional elastic waveelement of FIG. 2. FIGS. 5A and 5B illustrate a comparative example inwhich the reinforcement electrode 40 is only in contact with andelectrically connected to the upper connection wiring 31.

FIGS. 6A and 6B illustrate a cross-sectional view and corresponding planview, respectively, of one example of an embodiment of the elastic waveelement 60 in which the upper connection wiring 31 and the lowerconnection wiring 32 are in contact with and electrically connected toeach other.

FIGS. 7A and 7B illustrate a cross-sectional view and corresponding planview, respectively, of another example of an embodiment of the elasticwave element 60 in which only the lower connection wiring 32 is incontact with and electrically connected to the reinforcement electrode40.

For each of these examples, the reinforcement electrode 40 is made ofAluminum (Al), the upper connection wiring 31 is made of an Aluminumalloy, the lower connection wiring 32 is made of Molybdenum (Mo), andthe total contact area between the reinforcement electrode 40 and theconnection wiring 30 is 400 μm².

FIG. 8 shows the measurement results of the contact resistance per unitarea between the connection wiring 30 and the reinforcement electrode40. Five measurement points are plotted per each of FIGS. 5A-7B in FIG.8. As shown in FIG. 8, the contact resistances per unit area of theembodiments of FIGS. 6A-B and 7A-B are lower than the contactresistances per unit area of the comparative example of FIGS. 5A-B. Thisis because the oxide film formed on the upper surface of the upperconnection wiring 31 during the thin film processing increases thecontact resistances per unit area between the reinforcement electrode 40and the connection wiring 30. In addition, the contact resistances perunit area of the embodiment of FIGS. 7A-B are lower than the contactresistances per unit area of the embodiments of FIGS. 5A-B and 6A-B.This is because the oxygen affinity of the lower connection wiring 32(Mo) is less than the upper connection wiring 31 (Al alloy), such thatthe oxide film is less likely to be formed. Furthermore, comparing themeasurement values of the contact resistances per unit area shows thatthe measurement values for the embodiments of FIGS. 6A-B and 7A-B areless variable and more stable than the comparative example of FIGS.5A-B. Still furthermore, the variation of embodiment of FIGS. 7A-B isless than that of the embodiment of FIGS. 6A-B. This shows that thegreater the contact area between the upper connection wiring 31 on whichthe oxide film is likely to be formed and the reinforcement electrode40, the more variable are the measurement values of the contactresistances. Therefore, configuring the connection wiring 30 accordingto certain embodiments such that at least the lower connection wiring 32is in contact with and electrically connected to the reinforcementelectrode 40 reduces the contact resistance between the connectionwiring 30 and the reinforcement electrode 40. As a result, the electricloss in the connection wiring 30 can be reduced.

Examples of the resistance values per unit length of the connectionwiring 30 will be described below, comparing another embodiment of theelastic wave element 60 with a conventional elastic wave element, andwith reference to FIGS. 9A-11B, which illustrate examples of measuringthe resistance values per unit length of the connection wiring 30. Theconnection wiring configuration and the structure material of eachconfiguration are similar to the configuration described above andillustrated in FIG. 4. The lower connection wiring 32 is provided on theupper surface of piezoelectric body 50, and the reinforcement electrode40 is subsequently provided on the upper surface of lower connectionwiring 32.

FIGS. 9A and 9B illustrate a cross-sectional view and corresponding planview, respectively, of a comparative example in which there is nocontact between the reinforcement electrode 40 and the lower connectionwiring 32. The cross-sectional view of FIG. 10A and the correspondingplan view of FIG. 10B show an example embodiment in which the holeelectrode 70 has a diameter of 8 μm and extends through the upperconnection wiring 31 and the lower connection wiring 32. The holeelectrode 70 is filled with the reinforcement electrode 40, with thereinforcement electrode 40 and the side surfaces of the lower connectionwiring 32 being electrically connected to each other via the holeelectrode 70.

FIG. 12 shows measurement results of the resistance values per unitlength of the connection wiring 30. As shown in FIG. 12, the resistancevalues per unit length in the connection wiring 30 of the exampleembodiment illustrated in FIGS. 10A-B are lower than the resistancevalues per unit length in the connection wiring 30 of the comparativeexample illustrated in FIGS. 9A-B. The lower connection wiring 32 andthe reinforcement electrode 40 may be in contact with and electricallyconnected to each other even by a small area, and the result is that theelectric loss may be reduced in the connection wiring 30.

FIGS. 11A and 11B illustrate cross-section and plan views, respectively,of another configuration in which the hole electrode 70 is filled withthe reinforcement electrode 40 and is provided only in the upperconnection wiring 31 for the reinforcement electrode 40 to be in contactwith and electrically connected to the upper surface of the lowerconnection wiring 32. This configuration may also reduce the resistancevalue per unit length of the connection wiring 30 with respect to thecomparative example of FIGS. 9A-B, and may also achieve the reductioneffect of the electric loss in the connection wiring 30.

It is to be appreciated that the diameter of the hole electrode 70 isnot limited to the example of 8 μm discussed above, and that the effectof the reducing electric loss may be achieved by the lower connectionwiring 32 and the reinforcement electrode 40 being in contact with andelectrically connected to each other.

The pass characteristics of a ladder filter using an embodiment of theelastic wave element 60 and a ladder filter using the conventionalelastic wave element 6000 are described below.

FIG. 13 is a circuit diagram of one example of a ladder filter 400 usingan embodiment of the elastic wave element 60. As shown in FIG. 13, theladder filter 400 according to one embodiment includes a first serialresonator 301, a second serial resonator 302, a third serial resonator303, and a fourth serial resonator 304 serially connected between aninput terminal 201 and an output terminal 202. A first parallelresonator 305 and a second parallel resonator 306 are connected at oneend between the first serial resonator 301 and the second serialresonator 302 and connected at the other end to the ground. A thirdparallel resonator 307 and a fourth parallel resonator 308 are connectedat one end between the third serial resonator 303 and the fourth serialresonator 304 and connected at the other end to the ground. Each of theresonators 301, 302, 303, 304, 305, 306, 307, and 308 may include theelastic wave element 60.

According to one embodiment, both ends of each of the IDT electrodes ofthe resonators of the ladder filter 400 are provided at a single portionwith the hole electrode 70, as shown in FIG. 10B, whereas thecomparative example is manufactured having no hole electrode 70. Thepass characteristics for each ladder filter are compared in FIG. 14.

FIG. 14 shows measurement results of the pass characteristics in theladder filter 400. As shown in FIG. 14, the ladder filter of the exampleembodiment may enhance the attenuation amount in the passband and mayreduce the minimum insertion loss in the passband with respect to thatof the comparative example.

Embodiments of the elastic wave element discussed herein are useful inconfigurations of a ladder filter and/or in various electronic devices,such as a cell phone.

Having described above several aspects of at least one embodiment, it isto be appreciated various alterations, modifications, and improvementswill readily occur to those skilled in the art. Such alterations,modifications, and improvements are intended to be part of thisdisclosure and are intended to be within the scope of the invention.Accordingly, embodiments of the methods and apparatuses discussed hereinare not limited in application to the details of construction and thearrangement of components set forth in the preceding description orillustrated in the accompanying drawings. The methods and apparatusesare capable of implementation in other embodiments and of beingpracticed or of being carried out in various ways. Examples of specificimplementations are provided herein for illustrative purposes only andare not intended to be limiting. Also, the phraseology and terminologyused herein is for the purpose of description and should not be regardedas limiting. The use herein of “including,” “comprising,” “having,”“containing,” “involving,” and variations thereof is meant to encompassthe items listed thereafter and equivalents thereof as well asadditional items. References to “or” may be construed as inclusive sothat any terms described using “or” may indicate any of a single, morethan one, and all of the described terms. It is further to beappreciated that the terms indicating the perpendicular direction, theparallel direction, the depth direction and the like are used fordescriptive purposes to explain aspects of the present invention.Therefore, these terms do not designate the absolute directions and arenot intended to be limiting. The foregoing description and drawings areby way of example only, and the scope of the invention should bedetermined from proper construction of the appended claims, and theirequivalents.

1. An elastic wave element comprising: a piezoelectric body having anupper surface; an interdigital transducer (IDT) electrode disposed onthe piezoelectric body; a connection wiring disposed on thepiezoelectric body and electrically connected to the IDT electrode, theconnection wiring including a lower connection wiring and a upperconnection wiring disposed above the lower connection wiring; and areinforcement electrode disposed above the connection wiring, thereinforcement electrode being in contact with and electrically connectedto the lower connection wiring.
 2. The elastic wave element of claim 1wherein the connection wiring includes a hole electrode extending in adirection perpendicular to the upper surface of the piezoelectric body,the reinforcement electrode being electrically connected to the lowerconnection wiring via the hole electrode.
 3. The elastic wave element ofclaim 2 wherein the hole electrode extends through the upper connectionwiring and the lower connection wiring, a first diameter of the holeelectrode in the upper connection wiring being larger than a seconddiameter of the hole electrode in the lower connection wiring.
 4. Theelastic wave element of claim 1 wherein a material of the lowerconnection wiring is different from a material of the upper connectionwiring.
 5. The elastic wave element of claim 4 wherein an oxygenaffinity of the material of the lower connection wiring is less than anoxygen affinity of the material of the upper connection wiring.
 6. Theelastic wave element of claim 1 wherein the reinforcement electrode isin contact with and electrically connected to an upper surface of thelower connection wiring.
 7. The elastic wave element of claim 6 whereinthe upper connection wiring is divided by the reinforcement electrode ina cross section taken in a direction perpendicular to the upper surfaceof the piezoelectric body to provide first and second upper connectionwirings, the first and second upper connection wirings beingelectrically connected to each other via the reinforcement electrode. 8.The elastic wave element of claim 7 further comprising a thirdconnection electrode disposed on the piezoelectric body between thefirst and second upper connection wirings, the third connection wiringbeing covered with an insulation layer, and the reinforcement electrodeextending over the insulation layer.
 9. The elastic wave element ofclaim 7 wherein the lower connection wiring is divided by thereinforcement electrode in a cross section taken in the directionperpendicular to the upper surface of the piezoelectric body to providefirst and second lower connection wirings, the first and second lowerconnection wirings being electrically connected to each other via thereinforcement electrode.
 10. The elastic wave element of claim 9 furthercomprising a third connection wiring disposed on the piezoelectric bodybetween the first and second lower connection wirings, the thirdconnection wiring being covered with an insulation layer, and thereinforcement electrode extending over the insulation layer.
 11. Theelastic wave element of claim 1 wherein the IDT electrode includes alower IDT electrode and an upper IDT electrode provided above the lowerIDT electrode, a material of the lower IDT electrode being identical toa material of the lower connection wiring, and a material of the upperIDT electrode being identical to a material of the upper connectionwiring.
 12. A ladder filter including the elastic wave element ofclaim
 1. 13. An elastic wave element comprising: a piezoelectric bodyhaving an upper surface; a first interdigital transducer (IDT) electrodedisposed on the piezoelectric body; a second IDT electrode disposed onthe piezoelectric body; a connection wiring disposed on the uppersurface of the piezoelectric body and electrically connected to thefirst IDT electrode and the second IDT electrode, the connection wiringincluding a lower connection wiring and a upper connection wiringdisposed above the lower connection wiring; and a reinforcementelectrode disposed above the connection wiring, the reinforcementelectrode being in contact with and electrically connected to the lowerconnection wiring.
 14. The elastic wave element of claim 13 wherein thelower connection wiring is formed of a first material and the upperconnection wiring is formed of a second material, an oxygen affinity ofthe first material being less than an oxygen affinity of the secondmaterial.
 15. The elastic wave element of claim 13 wherein thereinforcement electrode is further in contact with and electricallyconnected to the upper connection wiring.
 16. The elastic wave elementof claim 15 wherein the connection wiring further includes a holeelectrode extending through the upper connection wiring and the lowerconnection wiring in a direction perpendicular to the upper surface ofthe piezoelectric body, the hole electrode having a first diameter inthe upper connection wiring and a second diameter in the lowerconnection wiring, the first diameter being larger than the seconddiameter, and the reinforcement electrode being electrically connectedto the lower connection wiring via the hole electrode.
 17. The elasticwave element of claim 13 wherein the connection wiring, including boththe upper and lower connection wirings, is divided by the reinforcementelectrode in a cross section taken in a direction perpendicular to theupper surface of the piezoelectric body to provide first and secondconnection wirings, the first and second connection wirings beingelectrically connected to each other via the reinforcement electrode.18. The elastic wave element of claim 17 further comprising a thirdconnection wiring disposed on the piezoelectric body between the firstand second connection wirings, the third connection wiring being coveredwith an insulation layer, and the reinforcement electrode extending overthe insulation layer.
 19. A ladder filter including the elastic waveelement of claim
 13. 20. An elastic wave element comprising: apiezoelectric body having an upper surface; a first interdigitaltransducer (IDT) electrode disposed on the piezoelectric body; a secondIDT electrode disposed on the piezoelectric body; a connection wiringdisposed on the upper surface of the piezoelectric body and electricallyconnected to the first IDT electrode and the second IDT electrode; andmeans for reducing electric loss in the connection wiring.